1. Field of the Invention
The present invention relates generally to surfaces for outdoor use and, more particularly, to a bound particulate rubber outdoor surface for use as an athletic playing or track surface.
2. Discussion of the Prior Art
It is known from U.S. Pat. No. 4,082,888 to Portin, to provide a cushioned protective outdoor surface formed of a composition including vulcanized rubber particles and a latex solution. In providing such a surface, the composition is mixed with water and a wetting solution and is applied wet to the underlying existing base surface in a single application such that the complete thickness of the surface is defined by the single layer of composition. According to this known method, once the protective surface layer is applied in the desired thickness, it is allowed to dry and take its final form.
Another known method for constructing an outdoor surface replaces the single layer application approach with a multi-layer approach, wherein a number of coating layers are sequentially laid down on top of a foundation surface and uniform layers of particulate rubber are applied to each coating layer after the underlying coating layer has dried and before application of the next succeeding layer.
Numerous drawbacks exist in the conventional methods. For example, where the single-layer surface application method is used in preparing an outdoor athletic track surface, it is common for the surface to be banked inward, and upon application of the single layer of composition, settling tends to occur due to the thickness and consistency of the composition. In addition to the problems accompanying settling per se, such an occurrence magnifies a further problem in the known methods wherein bubbling of the surface occurs due to the curing of the composition. This bubbling has been found to be most severe in regions where the composition is the thickest.
This problem of settling is also present in the multi-layer surface application methods, wherein each layer of coating material is applied to an underlying layer and then permitted to dry prior to application of the succeeding particulate rubber layer. Absent the particulate rubber, the wet coating layer flows more freely toward low spots in the underlying surface permitting thick regions to form in the layer and thus increasing the tendency for bubbling to occur.
The present inventor has previously employed a multi-layer surface application method differing from the afore-mentioned methods in that particulate rubber is applied over previously applied coating layers while the coating material is still wet. This method includes manually throwing particulate rubber onto the surface with shovels shortly after the underlying layer is applied so that the particulate rubber sinks into the coating material before the material dries.
Although this known method protects against settling of the coating layer, the method possesses certain drawbacks. For example, because the particulate rubber is manually applied, the method is labor intensive, requiring several workers to distribute the rubber.
Further, it is difficult to uniformly distribute the particulate rubber on the underlying layer because of the distances to which the particles must be thrown. Because it is not possible to walk on the wet underlying coating layer, reliance is placed on the skill of the workers throwing the particles onto the surface to insure that a uniform layer of rubber is applied.